The invention relates to a wellbore production logging tool, particularly for use in logging the properties of complex, multiphase and stratified flows encountered in such wellbores.
The majority of oil production today is from mature oil fields. Wellbores for producing oil from oil fields generally produce a mixture of oil, gas, water and suspended solids. Often the produced fluid is rich in water, particularly from mature oil fields.
It has long been known that accurate production logging can give precious information about the properties of the fluid in a wellbore. Interpretation of any resulting data can be used to provide information on a wide variety of aspects of the performance of a wellbore.
In particular, it is highly desirable to identify the locations of entry ports for oil, gas and water respectively. Once the location of a major water entry port has been found, say, then remedial operations can be carried out on the wellbore, potentially resulting in significant increases in oil production.
However, in some wellbore environments, particularly those found in highly deviated wellbores, such as complex multiphase and stratified flows, it is difficult or impossible to extract useful logging data with known techniques.
Baldauff et al, “Profiling and Quantifying Complex Multiphase Flow”, Oilfield Review, Autumn 2004, pp. 4-13, discloses a wellbore production logging tool which comprises a plurality of spinners, optical and conductivity sensors, which provide detailed information of phase profiles in a wellbore, even in highly stratified flows encountered in horizontal or near-horizontal wells. As with other known devices, the sensors are not mounted for rotation with respect to the shaft.
Whilst such a device can cope with a complex fluid environment, it nevertheless suffers from known production logging problems such as multiple sensor feedthroughs. Furthermore, loggers of this type can give erroneous readings in multiphase flows due to the problem of droplet sticking on the sensors themselves.
There therefore remains a need to provide improved production logging devices and methods.